This invention relates to accelerated polymerizable compositions comprising compounds containing moieties capable of free radical polymerization, organoboron compounds capable of forming free radical generating species capable of initiating free radical polymerization and adhesives based on such compositions. In another embodiment the invention relates to a method of polymerizing compounds containing moieties capable of free radical polymerization and to methods of bonding substrates using such compositions.
Low surface energy olefins such as polyethylene, polypropylene and polytetrafluroethylene have a variety of attractive properties in a variety of uses, such as toys, automobile parts, furniture applications and the like. Because of the low surface energy of these plastic materials, it is very difficult to find adhesive compositions that bond to these materials. Adhesives have been developed for bonding to these plastics. A series of patents issued to Skoultchi, U.S. Pat. Nos. 5,106,928; 5,143,884; 5,286,821; 5,310,835 and 5,376,746; Zharov et al., U.S. Pat. Nos. 5,539,070, 5,690,780 and 5,691,065; Pocius, U.S. Pat. Nos. 5,616,796; 5,621,143; 5,681,910; 5,686,544; 5,718,977 and 5,795,657; and Sonnenschein et al. U.S. Pat. Nos. 6,806,330; 6,730,759; 6,706,831; 6,713,578; 6,713,579 and 6,710,145 (all incorporated herein by reference) disclose polymerizable acrylic compositions which are particularly useful as adhesives wherein organoboron amine complexes are used to initiate cure. It is disclosed that these complexes are useful for initiating polymerization of adhesives which bond to low surface energy substrates.
Many of the disclosed compositions polymerize more slowly than is desired for use in industrial processes. This results in processes which exhibit low productivity. Jialanella, U.S. Patent Publication 2005-0137370 A1 discloses that the addition of cure accelerators to the above described compositions wherein the cure accelerators comprise compounds containing quinone structures; or compounds containing at least one aromatic ring and at least one, preferably two, substituents on the aromatic ring selected from hydroxyl, ether and both wherein the two substituents are located either ortho or para with respect to one another, and a compound having a peroxy moiety. The accelerators described function well with the disadvantage is that the use of such compounds adds an additional component to the formulations. The use of additional components adds cost to the formulations.
Therefore, there is a need for adhesive systems that are capable of bonding to low surface energy substrates which cure rapidly and do not require the addition of another component.